Prevalence of pertussis in Fukuoka: incidence and MICs of antibiotics for Bordetella pertussis isolate

Abstract

For bacteriological examinations of whooping cough patients, nasopharyngeal specimens were directly inoculated on the cyclodextrin solid medium (CSM) supplemented with 5 micrograms of cephalexin (CEX) per ml. The inoculated plates were cultured in an incubator at 35 degrees C for 3 to 7 days. During the period from 1990 to 1993, B. pertussis (43 strains) and B. parapertussis (1 strain) were isolated from 145 whooping cough patients and 34 relatives. B. pertussis were isolated sufficiently in June to December during the year. It was suggested that during this period epidemics of whooping cough occurred. All isolates of B. pertussis had K antigen consisting of 1, 3, and 6. The determination of minimal inhibitory concentrations (MIC) of antibiotics to B. pertussis was carried out by the micro dilution technique modified from the standard methods. The Stainer-Scholte broth, supplemented with heptakis (2,6-O-dimethyl) beta-cyclodextrin, was used for dilution of the drug, and also for cultivation of bacteria. For determining susceptibility of bacteria to antibiotics, twenty seven isolates of B. pertussis and one of B. parapertussis were precultured on CSM at 35 degrees C for 2 days. The turbidity of broth cultures was adjusted to that of McFarland no. 0.5, and diluted to the concentration of 10(6) CFU/ml. One hundred microliters of these suspensions were added to 25 microliters of each antibiotic solution. After incubation for 3 days at 35 degrees C, the turbidity of the bacteria was read macroscopically for determining the MICs. On the other hand, we compared the agar dilution MICs of 23 antibiotics to the broth microdilution MICs for 27 B. pertussis isolates.(ABSTRACT TRUNCATED AT 250 WORDS)